org.apache.tika.sax.TaggedContentHandler Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.tika.sax;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
/**
* A content handler decorator that tags potential exceptions so that the
* handler that caused the exception can easily be identified. This is
* done by using the {@link TaggedSAXException} class to wrap all thrown
* {@link SAXException}s. See below for an example of using this class.
*
* TaggedContentHandler handler = new TaggedContentHandler(...);
* try {
* // Processing that may throw an SAXException either from this handler
* // or from some other XML parsing activity
* processXML(handler);
* } catch (SAXException e) {
* if (handler.isCauseOf(e)) {
* // The exception was caused by this handler.
* // Use e.getCause() to get the original exception.
* } else {
* // The exception was caused by something else.
* }
* }
*
*
* Alternatively, the {@link #throwIfCauseOf(Exception)} method can be
* used to let higher levels of code handle the exception caused by this
* stream while other processing errors are being taken care of at this
* lower level.
*
* TaggedContentHandler handler = new TaggedContentHandler(...);
* try {
* processXML(handler);
* } catch (SAXException e) {
* stream.throwIfCauseOf(e);
* // ... or process the exception that was caused by something else
* }
*
*
* @see TaggedSAXException
*/
public class TaggedContentHandler extends ContentHandlerDecorator {
/**
* Creates a tagging decorator for the given content handler.
*
* @param proxy content handler to be decorated
*/
public TaggedContentHandler(ContentHandler proxy) {
super(proxy);
}
/**
* Tests if the given exception was caused by this handler.
*
* @param exception an exception
* @return true
if the exception was thrown by this handler,
* false
otherwise
*/
public boolean isCauseOf(SAXException exception) {
if (exception instanceof TaggedSAXException) {
TaggedSAXException tagged = (TaggedSAXException) exception;
return this == tagged.getTag();
} else {
return false;
}
}
/**
* Re-throws the original exception thrown by this handler. This method
* first checks whether the given exception is a {@link TaggedSAXException}
* wrapper created by this decorator, and then unwraps and throws the
* original wrapped exception. Returns normally if the exception was
* not thrown by this handler.
*
* @param exception an exception
* @throws SAXException original exception, if any, thrown by this handler
*/
public void throwIfCauseOf(Exception exception) throws SAXException {
if (exception instanceof TaggedSAXException) {
TaggedSAXException tagged = (TaggedSAXException) exception;
if (this == tagged.getTag()) {
throw tagged.getCause();
}
}
}
/**
* Tags any {@link SAXException}s thrown, wrapping and re-throwing.
*
* @param e The SAXException thrown
* @throws SAXException if an XML error occurs
*/
@Override
protected void handleException(SAXException e) throws SAXException {
throw new TaggedSAXException(e, this);
}
}